There are many ways to form rigid packaging containers. These may be formed by conversion of a plastic sheet for example, or a metal or paper composite via solid phase pressure-forming and solid phase stretch forming melt thermal processes and the like. Oftentimes, it is necessary or desirable to manufacture containers which have a "rolled lip" or flange which extends from the top of the side wall of the container for various purposes. An example of such a rolled lip is found on a "stadium" cup which is used to drink various beverages. The "rolled lip" may be useful for packaging of various dairy products, frozen foods, meat, fish, poultry and the like. Some type of an outer lip or flange which is rolled under is advantageous for various reasons. One of the reasons for this is that the rolled underlip protects the drinker of the beverage from cuts due to the sharp edge of the lip which is not rolled under. In addition, the rolled lip facilitates packaging and wrapping of the various containers for holding foods and beverages. For example, it may be desirable to wrap the container with a see through plastic film for packaging and storage on the shelf of supermarkets. Conventional lips which are not rolled under result in oftentime sharp and jagged edges which may puncture the film which is used to wrap over the top of the article and which is usually wrapped underneath the lip edge.
In producing a "rolled lip" container, it has been necessary that the production of the rolled lip be in a separate, secondary lip rolling step. Heretofore, a plastic article was made with a lip which was generally perpendicular to the side wall of the vessel or container and then in a second step the lip rolled under to create the appropriate rolled angle to facilitate downstream use. This second step of forming the lip into a rolled configuration has been time consuming and unwielding, not to mention expensive.
In past attempts to produce a molded article which has a "rolled lip" without the necessity of a separate rolling step, the part had to be shaped with the rolled lip and at the time the excess material was to be trimmed from the part. The trimming of the part at about the lip portion of the shaped part resulted in a flattening of the lip during the trimming process. This is because the trimming process has occurred with the top or concave part of the shape remaining in an upright position so that when the cutter edge press down upon the edge of the "rolled lip", the lip, as it was cut, flattens substantially to make a separate lip rolling step necessary.